apply_filters( 'update_welcome_subject', string $subject )

1732	 * Filters the subject of the welcome email sent to the site administrator after site activation.1733	 *1734	 * @since MU (3.0.0)1735	 *1736	 * @param string $subject Subject of the email.1737	 */1738	$subject = apply_filters( 'update_welcome_subject', sprintf( $subject, $current_network->site_name, wp_unslash( $title ) ) );1739 1740	wp_mail( $user->user_email, wp_specialchars_decode( $subject ), $message, $message_headers );1741 1742	if ( $switched_locale ) {1743		restore_previous_locale();1744	}